Converting light emitting objects from Cycles Render to Blender Render
I did some changes to your scene. The strange artefacts result from the high emit value and the curves themselves.


I adjusted emit value to 15 instead of 1000.
Give the curves some extrusion. No neon light is total flat, it has some depth. A value of 0.001 works great.
I added some ambient occlusion. A value of 0.008 makes the scene less dark but preserves the night mood...